c99 [ flag... ] file... –lm [ library... ] #include <math.h> double exp2(double x);
float exp2f(float x);
long double exp2l(long double x);
These functions compute the base-2 exponential of x.
Upon successful completion, these functions return 2x.
If the correct value would cause overflow, a range error occurs and exp2(), exp2f(), and exp2l() return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
If x is NaN, a NaN is returned.
If x is ±0, 1 is returned.
If x is −Inf, +0 is returned.
If x is +Inf, x is returned.
These functions will fail if:
The result overflows.
If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the overflow floating-point exception will be raised.
An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.
See attributes(5) for descriptions of the following attributes: